Effect of different treatments and SiO2/PVDF coatings on morphology and wettability of electrospun polyamide 6 membranes

The electrospun polyamide 6 (PA6) membranes are treated with different methods. The rough surfaces with different protuberances size and the fiber diameter are prepared by wet, dry heat, wet heat, and ethanol treatments under relaxation, and the formation mechanisms are analyzed. A relative stable structure of PA6 membrane is also prepared by ethanol treatment under tension, and its structure is as same as the untreated membrane. The dynamic water contact angles (WCAs) of the treated membranes are measured. The starting WCA of the membrane with wet heat treatment under relaxation is 90.95 degrees, which is larger than those of wet, dry heat, and ethanol treatments under relaxation. The effects of surface morphologies with different treatments on wettability are analyzed. For obtaining hydrophobicity, the membrane with wet heat treatment under relaxation was coated by polyvinylidene fluoride (PVDF). The WCA of the membrane increases to 127.1 degrees after coating. From another point of view, the WCA of the PVDF/treated PA6 membrane is much larger than that of the pure casting PVDF membrane, which means the rough surface of the treated PA6 membrane can improve the hydrophobicity of the PVDF membrane. Furthermore, the membrane is endowed with superhydrophobicity (WCA of 153.5 degrees) after being coated by SiO2/PVDF due to the multilevel structured surface roughness. It is a relative low cost and convenient operation method to prepare the superhydrophobic material. The results provide a novel preparation method of the superhydrophobic material and a treatment method of the electrospun PA6 membrane to obtain a stable structure. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48804.